The Bloc is allowed on National TV even though it's leader has no interest in becoming prime minister, and they care more about the "Nation" Quebec more than the rest of Canada. The reason being that these are media events designed to introduce voters to the men and women who are running to be the prime minister.
It is a matter of cultural reasoning which allows representation from every belief and culture throughout the country, that gave the Bloc a chance to voice their goals and agendas.
The leader of the Bloc has no interest or plan to lead Canada in any way, which shows very clearly in their selection of candidates for their party in Quebec only.
Bloc leaders are indifferent and often bitingly sacarstic towards Canadian politics as its party are primarily committed to severing Quebec from Canada completely.
It also support the provincial government bills 21 and 96. Bill 21 bans public servant from wearing headscarves and turbans, Bill 96 defines French as the only official language of Quebec and thus the definition of Quebec, as the nation for Quebecois people.
The bloc leader also demanded a couple of things for the would-be prime minister namely more no-strings attached funding for health care and also an openly discriminatory, French first immigration system. It just wants to ensure that people who wants to settle or immigrate to live in Quebec, need to be able to speak French.